Abstract:
Land degradation caused by soil erosion is one of the most serious environmental problems affecting
resources in mountainous areas of developing countries, particularly in sub-Saharan Africa. In
Ethiopia, to combat this threat, various soil and water conservation interventions have been
implemented. However, the effectiveness of SWC practices has not been well investigated in this
particular watersheds. Therefore, this study was conducted at the upper Awash watershed, Dendi
District, West Showa, Oromia, Ethiopia to evaluate the effect of physical SWC and slope gradients on
selected physicochemical properties of soil. For this study, two kebeles (Awash bole and Gare arera)
were selected purposively from the district based on their greater contribution to the watershed and
the availability of old physical SWC practices (terraced). A total of six composite soil samples were
collected from the top 20 cm of soil depth, replicated three times, and selected physicochemical
properties were analyzed in Ambo university laboratory by following national soil sciences
laboratory procedures. The results of the study showed that bulk density, soil organic matter, soil
organic carbon and cation exchanging capacity were significantly (p<0.05) different on farms
conservd (terraced) compared to the non-conserved (not terraced) plots. However, under slope
gradients, only SOM, SOC and CEC showed a significant p<0.05) difference. The parameters which
did not show significant differences with treatment and slope gradients were soil textures (clay, silt,
and sand), pH, EC, total nitrogen, available phosphorus and all exchangeable cations (Ca2+, K+, Na+,
and Mg2+). Even if other soil physicochemical properties did not show a significant(p>0.05)
difference, almost all soil parameters had a numerical difference with respect to treatments and slope
gradients in the watershed. In a conclusion, physical SWC (terracing) affected selected soil
physicochemical properties under the study area. Therefore, the area without SWC structure should
have applied different soil fertility management, to enhance soil fertility and productivities on the
cultivation area of the watershed
